Monomers chirality

Crass-Snking monomer Chiral monomer Poragemc softenl Polymefizafon initiator... 

Itsuno synthesized supported aminoalcohols 111-113 (Scheme 57) [104] and N-suUbnylamino acid 114 [105-107] (Scheme 58) by radical suspension copolymerization of the corresponding monomer chiral styryl aminoalcohols and styryl sulfonylamino acid derivatives with styrene and eventually with a crosslinker. 

Production and applications of chiral PHA monomers Chiral PHA monomers are mostly difficult to make chemically. If a large-scale application on certain PHA monomers can be found, it will increase the PHA values ... 

Figure 18 Synthesis of chiral LC copolymers by copolymerization of (1) nematogenic monomer with (2) chiral mesogenic monomer and with (3) chiral nonmesogenic monomers. Chirality of monomers is marked by an asterisk.

Polymers can have similar chiral effects as the corresponding monomers. Chiral centers in the wing groups or in the mesogenic groups can cause cholesteric and ferroelectric phases very similar to Section 4.3.1. However, polymers can have additional positions and effects of chirality. Chirality can be located in the backbone or in spacer groups, chiral dopants can be fixed by copolymerization, and cholesteric networks can be filled with guest compounds, etc. 

In other optically active polymers, as well as in some polymers from achiral monomers, chiral structures, characterized by all isomorphous helical chains in the unit cell, have been found. For instance, in isotactic poly(5-methyl-l-hexene) [94], isotactic poly(ubutylacrylate) [95], and optically active isotactic poly((S)-5-methyl-l-heptene) [94b,c], chiral pseudo-hexagonal or tetragonal packing with isomorphous 3/1 or 4/1 helical chains have been found. 

Ferroelectric side-chain liquid crystal polymers (fLCPs) have been synthesized only recently. (see Chapter 8). Because of the dilution of chiral side chains in the backbone matrix, the spontaneous polarization is weaker than in the monomer chiral smectics, although Kapitza and others recently reported polysiloxane-based fLCPs with spontaneous polarization comparable to that observed for monomer liquid crystals. 

Oligomer (Section 14 15) A molecule composed of too few monomer units for it to be classified as a polymer but more than in a dimer trimer tetramer etc Oligonucleotide (Section 28 6) A polynucleotide containing a relatively small number of bases Oligosaccharide (Section 25 1) A carbohydrate that gives three to ten monosacchandes on hydrolysis Optical activity (Section 7 4) Ability of a substance to rotate the plane of polanzed light To be optically active a sub stance must be chiral and one enantiomer must be present in excess of the other... 

For the 1,2- and 3,4-addition, a chiral carbon (marked by an asterisk) is formed which has an R or 3 configuration, but there is no net optical activity, because equal amounts of the R and S configurations are formed. The R and S configurations along the polymer chains lead to diastereomeric isomers called isotactic, syndiotactic, and atactic. In isotactic polyisoprene all monomer units have the same configuration as illustrated for isotactic... 

Another chiral titanium reagent, 11, was developed by Corey et al. [17] (Scheme 1.24). The catalyst was prepared from chiral ris-N-sulfonyl-2-amino-l-indanol and titanium tetraisopropoxide with removal of 2-propanol, followed by treatment with one equivalent of SiCl4, to give the catalytically-active yellow solid. This catalyst is thought not to be a simple monomer, but rather an aggregated species, as suggested by NMR study. Catalyst 11 promotes the Diels-Alder reaction of a-bro-moacrolein with cyclopentadiene or isoprene. 

Based on chiral functional monomers such as (15), MICSPs can be prepared using a racemic template. Thus, using racemic A-(3,5-dinitrobenzoyl)-a-methylbenzy-lamine (16) as template, a polymer capable of racemic resolution of the template was obtained [67]. Another chiral monomer based on L-valine (17), was used to prepare MIPS for the separation of dipeptide diastereomers [68]. In these cases the configu-... 

The asymmetric substitution pattern of most monomers means that addition gives rise to a chiral center and their polymers will have tacticily (Section 4.2). 

Transition metal coupling polymerization has also been used to synthesize optically active polymers with stable main-chain chirality such as polymers 33, 34, 35, and 36 by using optically active monomers.29-31 These polymers are useful for chiral separation and asymmetric catalysis. For example, polymers 33 and 34 have been used as polymeric chiral catalysts for asymmetric catalysis. Due... 

Okamoto and his colleagues60) described the interesting polymerization of tri-phenylmethyl methacrylate. The bulkiness of this group affects the reactivity and the mode of placement of this monomer. The anionic polymerization yields a highly isotactic polymer, whether the reaction proceeds in toluene or in THF. In fact, even radical polymerization of this monomer yields polymers of relatively high isotacticity. Anionic polymerization of triphenylmethyl methacrylate initiated by optically active initiators e.g. PhN(CH2Ph)Li, or the sparteine-BuLi complex, produces an optically active polymer 60). Its optical activity is attributed to the chirality of the helix structure maintained in solution. 

Some progress has also been achieved in the use of chiral polymer films at electrodes. Conductive polythiophenes containing optically active substituents in the 3-positions were prepared by electropolymerization of suitable monomers without apparent lc s of optical activity The polymer of exhibits distinct... 

Thus, this first example of stereoselective radical reaction, initiated with the system based on Fe(CO)5, shows opportunities and prospects of using the metal complex initiators for obtaining the stereomerically pure adducts of bromine-containing compounds to vinyl monomers with chiral substituents. 

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